Magnetically fired ignition device



Jam l, 1952 J. vl MCNULTY MAGNETICALLY FIRED IGNITION DEVICE Filed Nov. 16, 1948 Patented Jan. 1, 1952 UNITED STATES PATE BVI? OF F l C E MGNEII'C'AIZEY FIRED IGNITION DEVICE John'h V. McNulty;. Norwich; N2V Y., assigner to Gemerall Iia'boratoryt Associates, Inc. Norwich.. Ni, Y1, a: corporation; of#` N ewa York:

AppiicationNvemlerl, 19.48 Serial No..60262 vice= and' more particularlyf to` aff. sparki ignition: device for directv` expansion. type engines;v es gn.,

scr-calle'd'iet engines; Y

TheI adventl of extensivel useof direct? expan'; sion typeengines has-introduced manyfnevv prohlemsas-y comparedf to tliosefacedi with the? con;-4 ventional reciprocating type inter-nab combustion` engines: Aside from the differences`- inA mechane ical structure, one important". differenceiis that" the' directf' expansion engine sometimes: utilizes fuels of lowert gradesj and' l'sser"volati1it5r and.- consequentlyrequires a higher energy* spark: for ignition; Also, indirect expan'siontypeen'gines; after initial ignition there isk no'i need' forreeure ringf ignition, as the' fuel' is fed directly," into@ a combustion' chamber which is at? all.v tnesunderl a: state-of"ignition. Since lowengrade fuelstandY fuels of lesser volatility' are' sometimes' used, 'itis necessaryto impart greaterenergyto the spark,t in order that ignition; may`v bef readilyf ac'come .plishedi A purpose of this invention, therefore;. is to provide anI ignitionv device' that: will@ provide- A a suitable sparkfor ignitiontof said lowerfgrade: fuels and', in which the energyprox/ridad;l atfthe` spark gap is` substantially greater: than=thatfpruf vided in the conventional ignitionY systemsg. l

The use of` lower grade fuelsi leads: tos other1` difficulties: Al greater amount: of? carbon and Waste products are= deposited'. in thev combustionf chamberfa'nd on the ignition' device; atterrignitiony which' Will" rapidly' foul` conventionalspark ignition devices andN render them4v less efficientiv orJ inoperative for-subsequent ignitions: A further-4 purpose ofthis invention, therefore; isto provide at sparkf ignition devicef that: will; bee relatively impervious tor carbon deposits; on theL electrodes: as ai determinant?. of? eicient; operation; and-: in: addition to provide a'device .which WillLkeep :said carbon deposits-to' a minimum;

The-.-v conventional? ignition: devices;- as. used: in, reciprocating" typex internal combustion engines;- must; of' necessity, have.a:tirningsysternctorregnaA laten then order' ofV 'ring; In:v ai directa expansion; type*y engine there is no: need'. for" a; crumbeiserne;l timing-system; as once= the fuelf islignited,4 it*y stay ignited untill' the'4 suppl-yj fuel-` iseither" exhausted or shut4 of' Av furthe? object oftlfiisr invention; therefore; is tof-provifdean'entire-:ly selfL timed ignition system; eliirnnatingl the needi for'y a cumbrous timing; system; andl t"o\providefor manua'lcontrol of; the;v actuation off said, ignition System.

' Siilcegreaterenergyfis neededatl'the.electrodesll tofignitetnelowenaradeeiuelsfandifuels Qfflessei" volatility` utilized in direct' expansion type en-VA thus'r reducinginsulationfproblems Atofa minimum.

The` advent of*E directexpansionl type' engines`r as a primary sourceI of.- power for' aircraft has-1 greatlyincreased'the' altitude range of the stand-- ard typesof' aircraft.- The' changes in altituder and the variationsfin densityof the atmosphere'. accompanyingthe same, cause variations in. breakdown'l voltage and ashover between undesiredv points;` The normal' ignitionsystem isf thereforeA subject'v toi inherent troubles at high altitudes; and willnotr function at a high peak of'efciency.. A furtherobje'ct of` thisinvention,. therefore; isv to provide a` spark'ignition systen'if. thatwill work at a high degree ofreciency` at" all altitudes.

In addition to: considerations of' altitudef and'k t;,fpesof'filel,` a number ofother'factorscontribute to malte.v theN ignitionY requirements: of:v direct* ex. pansion': engines' dierentirom those off the con-- ventional reciprocating type: These other fac f torsiincludeitemperatura air velocity, ramf pres sure; and" fuel ratio; when` they are considered.l along With the matters alreadylinentioned; it'has been found' that 'a' higher' spark ener ;y is: ref quired' tol ei'ect ignitiontin enginesof this typeV as contrastedzvvith ordinary reciprocating engines:l The'y present invention is therefore designedY to satisfy-these requirements, inv a: particularlyI re-1 liable manner; indeed the reliability andv sure+ nessi'l off' operation. of thepresenty ignition device are very'` importanti because ofv sol-called' blow-- outs, i; e. extinguishment'ofzcombustion; that arefy apt to take place* in'. present. types oi" jet.` engines.'A and the. likef. With sustained, burning acliievedf` only under-favorable conditions; it is oftentneces=- sary to rer-ignite" the fuel While the aircraft,xforf example, is in iiiglltlv The present device? re"- spondsfpromptlyf and eiectively; by af simplecire cuit-closingl operation, to`r provide such reignietro'de: This 'heatingr of thev` electrodes might; be;

suicient to cause thel electrodes to glow, and this consequent high temperature of the electrodes together with the impurities present in lower grade fuels has led to a very short life for the standard type electrodes and sparking device as used in the conventional direct expansion type engine. A further object of this invention, therefore, is to provide a spark of low repetition rate with a consequent reduction of electrode temperature and the consequent longer life of said electrodes.

Referring now to the drawings:

Fig. 1 is a longitudinal section of one embodiment of the complete ignition device;

Fig. 2 is a transverse section on the line 2-2 of Fig. 1; and

Fig. 3 is a longitudinal section of another and presently preferred embodiment of the invention.

The invention may be identified as an improved ignition device for direct expansion type engines, and may be generally described as a break spark igniter, wherein current is caused to flow through the windings of a solenoid, building up a strong ma'fnetic field. The current path is then automatically broken due to the action of said magnetic field and the energy stored therein is dissipated in the form of an arc at the electrodes.

In Figs. 1 and 2 the electrical inout terminal I is mounted in an insulating member '2 in a sccket 3, which is, in turn, mounted in the upper cylindrical metallic housing 4, which is constructed of a metal of high permeability such as soft iron. The input terminal I is electrically connected to tbe windings of a solenoid 6 by an insulated lead 5 of suitable conducting material.

The solenoid winding 8 is concentrically mounted within said cylindrical housing 4 and is securely held in position by a fixed collar 1 and a xed bushing 8, both constructed of a suitable metallic material having a high permeability. The shaft of said bushing 8 extends into and forms a part of the core of said solenoid 5. The entire core of said solenoid winding 6 consists of a xed element and a movable element. The fixed element consists of the shaft of said bushing 8 and does not move with respect to the solenoid 6. The movable element comprises a tubular metallic shaft 9 of high permeability, separated from said solenoid 6 by a fixed layer of insulating material I0. Said core or shaft 9 is adapted to move in a direction parallel to the axis of said solenoid winding 8 and is normally held in the extended position. as shown in Fig. 1, by the spring 22. The spring 22, under compression, is mounted at one end on the shaft of the bushing 8, and is mounted on the other end on the bushing II. The latter is one of a pair of bushings II, I2 made of suitable insulating material, which are mounted concentrically within said tubular shaft 9 and serve as a mounting or sliding support for the shaft of the movable electrode I3. The normal position of the tubular shaft 9 is disposed to create a gap 32 between the end of said shaft 9 and the end of the shaft of the bushing 8. By way of example, for one type of device having the specific structure shown, tests have demonstrated that a gap of the order of .120 inches leads to satisfactory results.

The other terminal of the solenoid winding isY electrically connected to the conducting cap I4 of the terminal block 20, mounted on theinternal side of the annular section of said upper cylindrical housing 4, by aninsulated lead I8. The terminal block 28 consists of an insulatingr member I5 upon which is mounted said conducting cap I4. The electrode connecting rod I1. composed of suitable conducting material is electrically connected to said conducting cap I4 by an insulated lead I9. Thus through the above series of connections the electrode connecting rod I'I is electrically connected with the second terminal of the solenoid winding 6. The electrode connecting rod I1 is contained axially within a sleeve 2I made of suitable insulating material, and the assembly of the connecting rod I1 and insulating sleeve 2| is movably mounted axially within said bushing 8 forming the xed part of the core of the solenoid 6. The movable electrode connecting rod I1 contacts at one end the movable electrode I3 and terminates at the other end, in an insulated bushing I8. A compression spring 23,9munted at one end on an insulating bushing 24 which the conducting can I4 of the terminal block 20 carries, and mounted at the other end on the insulating bushing I8, keeps the electrode connecting rod I1 in iirm contact with the movable electrode I3. thus providing a direct electrical connection between sai-1 connecting rod Il and the movable electrode I3. Thus it is seen that there has been provided a direct electrical connection from the input terminal I, through the solenoid 6, through the electrode connecting rod I'I to the movable electrode I3.

The movable electrode I3 extends beyond the movable tubular shaft 9 forming part ofthe core of the solenoid 6 and extends through the lower cylindrical housing 25. The lower housing 25 i "in the preferred form of the invention as shown in the drawings, has a pair of flanges 26, having apertures 21 drilled therein adaptable as a mounting unit in a direct expansion type engine. The lower section of said lower housing 25 serves as a mounting for the fixed electrode 28 and as a ground for the entire device. The lower housing 25 is insulated from the cylindrical housing 4 by the insulating member 1A. The lower section of the movable electrode I3 is contained axially within a sleeve 29 movable in conjunction with said movable electrode I3. Said sleeve 29 and the movable electrode I 3 contained axially within said sleeve 29 are mounted to slide in bushings 30, 3| composed of suitable heat-resistant, electrical insulating material and being fixed in position with respect to said lower housing 25.

The invention is adapted to operate with either an alternating current or direct current source of power. For the purposes of example herein, however. the operation will be considered as if with a direct current source of power. The positive terminal of a battery 36 is directly connected to the input terminal I and the negative terminal of said battery 36 is connected through a switch 35 to the fixed electrode 28, either directly or through ground where the electrode 28 is, as shown, grounded and is at ground potential. As

the switch 35 is closed applying voltage to the cirwill have a zero value and the current will grad-j ually build up to its peak-value as determined by the circuitconstants. As the current builds up in its passage through the solenoid winding 8, a

ammassi through. the? housing: 4;. thebushing: 8, the" mov-'-V ablel sha-H719?`- andl` the: collarf Ii all. made of metal'. ofi high" permeability.. flux. will cause thef movable shaft to'A move towards the. bushing 8,. tending'v to closef the gan 32.` This.` movementisl continuallyresisted:byfthe spring ?ifwhich-rist'dis posed'.L to'. preventithezmovement'of the shaft Si untii'". :i1/magnetic: field of sunicient'strength to ourercome` the? tensionot" the. spring" 2'2.' hasf been: built up. As theux .reachesasuflbient strength" tof-movey said: tubular" shaft 9: by.' overcoming then tension ofth'e spring 92'; .said vti-ibularshaft '9 togetheriA witlrL the'. bushingsLl I I I2'` will: move as a unit:y Thebushing-"II has an' annularrecentacle recessed" thereinz. andi adapted to contain. a:

flange 1 34;.. mounted` on'v the. movable electrode I3."

attheextremity ot'said electrode' i3; The annuiar.l receptaclez. 33; isf adapted to'` permit'V the'r movement? oftheshazftig and.y tl'iefbushineV I li. I 2.- through a: slight* distance before contactingthe.: harige- 34 and.' causing. thefmovableV electrode I3" tofmove..

Asth'e" movable tubular shaft'lS togetherr'with the bushings if and. lZl moves in a direction to closeithe capaz', they annularreceptacle will move towards theiiangedsection 34. When the base of'said annui arf receptacle 3.3 contacts 'the ange 34l` on: themovable; electrode; I3, the current in f thesolenoi'd 'and the'resul'ting magnetic'fleld have built: up Quite" considerably, indeed preferably to oifneanthe'maxirnum;v The tubular core or shaft 9 has also Anew acquiredl considerable momentum, and.y for that reasonk and because: of the strong field. acting onzit; .iswell adapted4 to overcomeV the force.' of .both the springsi2.2',23; In consequence' as the' base.' ofthe recess33 strikesithfe'flange 34 on` thevl electrode .l 31, ther latter. assembly, together with the electrode connecting rod I1, is' moved smartly along' with' theicorememberg; Inpther words', theelectrode' I 3 is nowV moved :byithe kcore member' away from the fixed electrodeV :Zllbreak` inarl the contact between them: the momentum of the corememberis indeed preferablysuihcient to open. a gapv yof d'esirablysubstantial.- extent. between. the faces ofthe electrodes 43a; 28a.. When the movable electrode-Irthus'moves out of con@ tact from .the Vfixed electrode A28 (separatingV their faces, as stated) theenergizing or charging cirl cuit as described'above is-broken. andthecurrent ow through saidy circuit is. interrupted.. This interruption of currentflow causes the magnetic eld which had previously been built' un to collapse. The collapse of said magnetic' 'eid causes' the" current'to'- attempt to flowirr the interrupted circuiti' InA consequence: current willv iiowin saidcircuiti immediatel-ywausing an arc or' spark' to' bef'rmed across the' `gap between the'y movable electrode I andthe fixed :electrode 2'8"l as" theenergy' available in the collapsing :magnetic field'i's" dissipated.' i

.Afterv the energy? available" iii the'. magnetic. eld'lia's been dissipated' in the formiofl anarc'. between the movable.. electrodeV Iii and. thefixedelectrode 28:, the. electrodes.l will. again.. contacteach. otherV under the pressure of the. spring 22` andthe. spring 23. When the movable'electrode.- Iacontactsthexed electrode 28, the charging circuitnwill againbe completed,. current will ow causing a new; magneticfeld. to build*4 up and theiabovef: described cycle' will z repeat. itself; They axis of. t

' to the. winding 5 of electrode. 285 andi themovable: electroclef I3' serves:

to: permit: an greater'- magnetic` fieldf strengthl to:

lie-built up, with azconsequently greater; energy/ content in. the: resulting.v arc; and al'so.- serves; to'VL permit. thek tubular shaft" 9 to. gain enough. mo.-

mentumto provide.-a.widergaprbefore and dur--` ing; the arc-oven.. Itwill. be. understood that fifi the contacts open as soon as the core startsto. move:under the influence ofthe magnetic field, the energizing current, and thus the ield` itself, may not have risen-beyond a value far short of. saturation; whereas with the present construcir tion, the eurentA and field strength may'in'eiectz reach. a maximumV before the delayed contact f opening: takes place'. The openingand closing of thagapbetw'een the electrodes ata rate' deter.- mined. bythe repetition rate of thel above de! scribed. cycle. aids-n the. shaking loosel of any" carbon or. other` depositsv on the contact'v surfaces'v of the. eectrodes. with consequent increase. of: eiicencyi.

'llhearc-over.` normally occurs aftertheI mov#` able electrode. i 3` breaksv its contact with the xed. electrode 28 and is moving away from said fixed.'y

. electrode 28. The exact point atwhichv the ring will take place is a function of the magnetic field` strength,y the dielectric constant ofthe medium present in the gap between the electrodes,.and the spacing of the electrodes. Assuming 'the magnetic eld strength `to' be constant (which it.r

is for all practical purposes) ,.the pointat which the spark will jump the gap is determined by the distance between the` electrodes and the dielectric constant of the medium.- Since the dielectric constant` will vary with the altitude'of the device, the moving electrode I3 will pass, at some1 point in its movement, through the. optimumpoint'for arcing. Thus the invention. wllprovide asatistory spark at any altitude.

By way of specic example, with. an arrange# ment as shown in Figs. 1 and 2, very satisfactory' resultshave been obtained by utilizingV a gap spacing of approximately .120 inch for the gap' 32 between` the tubular shaft 9 and the bush-- p ing 8, and aispacing of approximately .G40 inchl for the gapsbetweenthe base of the annularrre-A ceptacle33 on the bushing i! and theange 34 onl the movable electrode I3.

Fig. 3 showslanother and presently preferred embodiment` of the invention,V which involves a simplified structure, easy to manufacture at-low cost and yet highly eicient in the attainment of'` thedes-ired results.- The device is shown` in vertical section: through its horizontal axis, viz. the solenoid winding 4h, corresponding The. winding' is surrounded by core structure including a cupshaped cylindrical housing 4i, a forward wall 42 andy a stud-like core member 43- projecting into' the centralcpening of the Isolenoid winding, from an inner plate 44 that isidispcsed adjacentthe rear-wall. of. the housing-4 I.. A. ,horizontally-slide* able-sleevev extends througha central opening I in: the front wall 42,"so as' toi constitute further"i A.core structure approachingr the` stud' 43, but' spacedfrom it in the manner of the-tubular'mai ber 9 ofv Fig. l relative to the bushing 8. The members 45t to inci'usive'constitute'the core or ma'gnetic1circuit of? the solenoid andY are conveniently' made of soft iron' or other suitable ma-A terialof high permeability.

Ai shallowscureshaped mountingplateA-'IL emcases. thea forward?. end.'v of: the. housed. stmcture 4 [if- 42 carries: a; proj ecting.` tubular: portion.

Thegdelattinfopeningsthefgapzbetweemthgxed; 75: 48::alig1redawitlii the .central clpeningfoffV the-solenoid Winding and the members 43, 45. An electrode mounting rod 50 is disposed within the tubular portion 48, being adapted to slide in a horizontal direction, along the central axis of the device through a sleeve of insulating material, preferably a refractory or like substance having good resistance to deterioration at very high temperatures.

At its outer extremity the rod 50 carries one spark electrode 52 adapted to abut the other spark electrode 53 mounted on the inner surface of a bail or arm 54 which projects from the tubular portion 48. It will be appreciated that the spark electrodes 52, 53 are shown in contact and are adapted to be broken, i. e. to produce a spark, when the rod 56 moves longitudinally away, viz. to the left as seen in Fig. 3. At its opposite or inner end the rod 50 carries an enlarged head or disc 56, sliding in a corresponding cylindrical recess in the member 45, the rod 56 itself traversing an opening 51 (in the member 45) of less diameter, and the structure of the member 45 thus providing a shoulder 58 facing the disc 56, but normally spaced from it as shown.

A coil spring 63 disposed, under compression, between the ends of the stud 43 and the head 56 of the electrode rod, normally keeps the electrodes 52, 53 closed. Another coil spring 6|, conveniently surrounding the spring B and a reduced portion of the stud 43 as shown, extends under compression between the inner end of the sleeve 45 and a cooperating shoulder 62 on the stud 43. The spring 6| serves to keep the sleeve or tubular core member 45 in its normal, outer position, where it rests against a flange 64 carried by the electrode rod 50.

The electrical connections of the several elements in the device of Fig. 3 are functionally the same as in Fig. 2, i. e. the solenoid winding 45 and the electrodes 52, 53 being connected in series across the terminals of the device, which consist of a grounded sleeve 66 and a central pin 61 surrounded by the sleeve but mounted in an insulating bushing 68. More specifically, one terminal of the winding 46 is connected to the pin 61, the other terminal of the winding being connected to the stud 43 and thence via a flexible lead 10 to the metal electrode rod 55 which terminates in the electrode 52. The other electrode 53 is connected through the metallic housing and mounting structure 48, 41, and the housing 4|, to the grounded sleeve 66.

To facilitate connections and afford an economy of parts, the forward plate 42 of the solenoid core structure is insulated from both the housing 4| and the mounting cup 41 by a channel-shaped ring 'l2 of insulating material around the circular periphery of the plate. The outer flange of the ring 12 also serves to space the plate 42 from the web of the cup 41. Thus in cooperation with the insulating sleeve 5|, the entire reciprocating assembly, along with the plate 42, is insulated from the grounded housing structure. The supplemental plate 44 is likewise insulated from the rear wall of the housing 4| by a layer 13 of insulating material, so that the stud 43 and the springs 63, 6|, which are in electrical contact with the reciprocating elements, are similarly insulated from the housing. It will be appreciated that the insulating members 12, 13 do not interfere appreciably with the magnetic ilux in the solenoid core, but afford a simplicity of structure while permitting the use of a continuously metallic outer housing which may be mounted at'ground potential.

-It will now be appreciated that the mode of operation of the apparatus of Fig. 3 is essentially identical with that of Figs. 1 and 2. Upon closing the circuit connecting a source of current (not shown) to the terminal 66, 61, the solenoid winding is energized, building up metallic flux in its core. 'The sleeve or tubular member 45 is thus caused to move inwardly, i. e. to the left as seen, in an attempt to close the gap between it and the stud 43, the force being sufficient to overcome that of the spring 6|. After the member 45 has travelled a distance equal to that between the head 56 and shoulder 58, the latter engages the head so that continuing travel of the member 51 then pulls the electrode rod 55 to the left, opening the electrodes 52, 53. Since by this time the flux in the magnetic circuit has built up near or to a maximum, interruption of the circuit causes a spark of correspondingly high energy to pass between the electrodes. After the magnetically stored 'energy has thus been dissipated in the spark (or arc) the latter interrupts itself and the parts return to their original position under the force of the springs 60, 6|. 'Ihe cycle of operations is then automatically repeated, and will continue to be repeated so long as the energizing circuit (cf. Fig. l) connected to the terminals 66, 61 remains closed. It will be seen that the device of Fig. 3 provides the same delayed opening of the electrodes, with the same high energy of spark, as described in connection with Fig. l, thus affording a peculiarly satisfactory ignition device for engines of the jet or direct expansion type. At the same time, the device of Fig. 3 is compact and is characterized by an advantageous simplicity of structure and economy of parts. It will be understood that in operation the mounting member 31 provides appropriate fastening to the wall of the engine chamber, into which the tubular portion 48 projects, for exposure of the electrodes 52, 53 within the chamber.

In accordance with the provisions of the patent statutes, I have herein described the principle of operation of this invention, together with the elements which I now consider the best embodiments thereof, but I desire to have it understood that the structure disclosed is only illustrative and the invention can be carried out by other means. Also, while it is designed to use the various features and elements in the combinations and relations described, some of these may be altered and modified without interfering with the more general results outlined as coming within the scope of the invention.

Iclaim:

1. A sparking device comprising a solenoid having an axial core opening, a movable, tubular core member comprising magnetic material and extending along the axis of the solenoid and into the opening from one end of the latter, said core member having its inner end normally within the solenoid and being adapted to be attracted further into thesolenoid, a. fixed core member of magnetic material extending into the opening oi the solenoid from the other end of the latter, said core members being disposed to provide an air gap between their inner ends inside the solenoid opening when the movable core member is in its aforesaid normal position, a xed spark electrode mounted outside the solenoid and beyond the outer end of the movable core member, a movable spark electrode normally disposed in contact with the xed electrode and having an operating rod' extending from said movable electrode into said movable, tubular core member, means for 're-J siliently urging said movable electrode against said fixed electrode, said rod having an enlarged portion within the tubular core member and the tubular core member vhaving internal shoulder means adapted to engage said enlarged portion, said shoulder means being spaced from the enlarged portion, when the tubular core member is in its said normal position, by a distance shorter than said gap, so that upon inward magnetic attraction of the movable core member inside the solenoid opening toward the iixed core member, the movable core member and its shoulder means first travel said distance and then the shoulder means engages the enlarged portion of the rod to separate the movable electrode from the fixed electrode.

2. A sparking device as described in claim 1, which includesmetallic housing structure at one end of the solenoid, supporting said fixed electrode and slidablvsupporting said rod'at'a locality beyond the outer.: end of the lmovablu core member, a metallic housing including portions of magnetic material tci'gprovide corresponding portions of an external uzip'ath around the outside of the sole noid betwee-'the core members, "saidf's'econd hous ing surrounding the solenoid and'f 'cooperating with the first housing structure to provide `a. complete enclosure for the solenoid andthe fixed and movable core members, and means including insulating material, for electrically insulating the aforesaid rod and movable electrodefrom both the aforesaid first housing structure and the second housing. 3-'1`Ar`sparking device as described -in claim 2, h the second housing includes a1 cylindrical of magnetic material surrounding the outefr sides of the solenoid, the device inciuding plate "members of magnetic materialgat the respe'tive ends of the solenoid for completing ux path -between the said cylindricaljportion and thejcofre members, and said insulatinglmeans comprisingzan insulating sleeve around the rod separati-rig'the latter from the first housing structure andthin members of insulating material disposed to separate the aforesaid plate members from the irst housing structure and second housing.

JOHN V. MCNULTY.

REFERENCES CITED? The gollowing references are of record Vin the 1e`ot this patent: i

UNITED STATES PATENTS Name Date Maillard e- `.-LMar.31, 1908 Torrens f.f. Jan. 5, 1909 Baehr Oct. 18, 1910 1,263,005 Truesdell Apr. 16, 1918 1,339,429 Truesdell May 11. 1920 

